Petrol-powered LMP1 cars have been given a number of performance tweaks ahead of the Le Mans 24 Hours.
Le Mans organiser the Automobile Club de l'Ouest has made the changes after analysing car speed in a bid to equalise performance between petrol and diesel machines.
Petrol LMP1s will now have their air restrictors increased in size by 0.3mm and be allowed to shed 10kg from their base weights in a bid to ensure that their performances fall within two per cent of the quickest diesel-powered car at Le Mans.
In the case of cars that are unable to lose any weight, a 0.5mm increase in air restrictor size will be permitted.
Petrol-powered cars will also benefit from a faster rate of refuelling, their hoses being increased by 10mm diameter, while diesel machines, such as the works Audi R18s and Peugeot 908s, have had their fuel hoses reduced by 0.3mm diameter.
Additionally, the older-spec, ORECA-run Peugeot that won the Sebring 12 Hours earlier this year, has had 15kg knocked off its base weight.
ACO sports manager Vincent Beaumensil said that the changes had only been now because there had not been sufficient data available for analysis by until after the recent Spa 1000km.
He believes the tweaks will allow petrol-powered cars to cover five laps more at Le Mans than in 2010 and will allow them to make the same number of fuel stops as leading diesel machines.
In LMP2, cars built to the cost-capped 2011 regulations will be allowed to increase the diameter of their fuel hoses by 3.5mm compared to the older models.
In the GTE class, the Lotus Evora has had its performance tweaked while a similar boost has also been applied to the Doran Ford GT that competes in the ALMS.